Food casings of regenerated cellulose are widely used for the production of various stuffed food products. Cellulosic casing for production of large diameter sausages such as bologna and the like generally are reinforced with a fibrous web. The present invention, however, is concerned primarily with thin walled unreinforced cellulosic casing as may be used in the production of small diameter sausages such as frankfurters and the like.
For convenience of handling, food casings which may be 20 to 50 meters or more in length are shirred and preferably compressed to produce what commonly are referred to as "shirred casing sticks". Such casing sticks are hollow cylinders about 20 to 60 centimeters in length. Shirring machines for producing these shirred sticks are well known in the art and are disclosed in U.S. Pat. Nos. 2,983,949 and 2,984,574 among others. Shirring and related technology also are described in the Noyes Data publication "Sausage Casing Technology" by Karmas (1974) at pages 259-347.
Cellulosic casing for the shirring operation is supplied in reels. The flat casing feed stock, drawn from a reel, is fed into a shirring machine where it is inflated with low pressure gas, usually air. The inflated casing is moved onto and along a mandrel and through an array of shirring rolls. In one form of shirring, the shirring rolls gather the casing about the mandrel into generally conical pleats nested one tightly against another. The inner folds of the pleats are formed against the mandrel and define the surface of an axial bore through the stick.
When a preselected shirred length has been attained, it is severed from the unshirred feed stock and moved longitudinally away from the array of shirring rolls for further processing. Such further processing may include, for example, a compaction operation where the shirred length is reduced and an operation where a closure is formed and inserted to stop or plug the bore at one end of the casing thereby forming a "closed" end. The other end of the casing is left open to permit mounting of the shirred stick onto a stuffing horn.
Severing of the last shirred end of the stick from the reel of casing feed stock has been accomplished both manually and by automatic means. Severing generally involves a tearing action. For example, U.S. Pat. No. 4,885,821 discloses a severing method and apparatus wherein a knife edge closes against the end face of a shirred stick. The knife edge pushes on the shirred stick while the feed stock is held. This tenses the feed stock casing so it tears along the knife edge where the feed stock joins the shirred stick.
However, tearing the casing, even along a knife edge, often results in one or more so called "shards" of casing attached to one or both the severed ends. A shard is produced when the ends of a tear or tears propagating around the casing do not meet but instead run past one another so a small neck of casing lies between the ends of the tear. Moreover, if tears initiate at several points along the knife edge, a plurality of shards may be produced.
Shards at the severed ends of the casing are objectionable because they may separate from the casing and become incorporated into the food product being stuffed into the casing. This is especially the case when using the casing for stuffing frankfurters. After a shirred stick is stuffed with a frankfurter emulsion, it is common for the operator to squeeze out or "milk" emulsion from the ends of the casing so the ends can be tied off. Shards at the end of the casing can rip free responsive to this procedure. Since the emulsion squeezed out of the casing is recovered and recycled, any shard of casing ripped off by the procedure may become incorporated into the emulsion supply.
Accordingly, it is most desirable to sever the shirred stick from casing feed stock in a manner which eliminates the formation of shards on the severed ends of casing.